Inertia type electromechanical sound transducing device



Aug. 27, 1957 w; KNAUERT-ET AL 2,804,509

INERTIA TYPE ELECTROMECHANICAL SOUND TRANSDUCING DEVICE Filed July 17. 1952 3 Sheets-Sheet 1 lillll 74 w. aw y? BY M 44,

g- 1957 w. F. KNAUERT El AL 7 2,804,509

INERTIA TYPE ELECTROMECHANICAL SOUND TRANSDUCING DEVICE Filed July 17, 1952 3 Sheets-Sheet 2 M ,gygggg BY .Z/V/MHALKO 1957 w. F. KNAUERT ET AL 2,

INERTIA TYPE ELECTROMECHANICAL. SOUND TRANSDUCING DEVICE Filed July 17, 1952 5 Sheets-Sheet 3 7/ I ll 1: 2-60 s #MW 0 2. A uk a WM H m w v4 5 Ml INERTHA TYPE ELECTRGMECHANKCAL SOUND TRANSDUCENG DEVICE William F. Knauert, Yonkers, and Ignatius Michaiho, flssining, N. i., assignors to Sonotone Corporation, Elmsford, N. EL, a corporation of New York Application .iuiy 1'7, 1952, Serial No. 2%,474

8 (Ilaims. (Cl. 179-1ti7) This invention relates to electromagnetic vibratory energy transducers, such as bone conduction receivers and throat microphones and the like and more particularly to junction elements of the cooperating magnetic core elements of such transducers.

In bone conduction receivers of the type widely used in hearing aids, such as described, for instance, in Greibach Patent Re. 21,030, a relatively massive magnetic core portion is resiliently carried in a floating vibratory condition by a bone coupled magnetic core portion or armature for producing therebetween a vibratory motion which causes the bone coupled core portion to transmit hearing inducing vibrations to hearing inducing bones of the user.

In such receivers, it is essential to provide a stop which prevents an excessive excursion of the floating core away from the bone coupled armature when the receiver is accidentally dropped, or like occurrence. In the past, such receivers had been provided with distinct stop elements for preventing such excessive excursions.

Among the objects of the invention are electromagnetic vibratory transducer structures wherein the cooperating core elements are arranged to be joined to each other in such manner that their junction element or elements also serve as a stop means which limits vibratory excursions between its opposite core portions to a fixed distance to assure that they are returned to their desired operative air gap spacing.

Although the present invention was evolved specifically to overcome difficulties encountered with hearing aid bone conduction receivers, the invention has wide application in connection with all types of electromagnetic vibratory devices having cooperating magnetic core portions which vibrate relatively to each other across a small operative gap, the critical spacing of which has to be maintained for satisfactory operation thereof.

The foregoing and other objects of the invention will be best understood from the following description of exemplifications thereof, reference being had to the accompanying drawings, wherein:

Fig. 1 is a vertical cross-sectional view of one form of a practical bone conduction receiver exemplifying the invention;

Fig. 2 is a cross-sectional view along lines 2-2 of Fig. 1;

Fig. 3 is a cross-sectional view, Fig. 2;'

Fig. 4 is a plan view of the electromagnetic structure of the same bone conduction receiver along lines 2-2 of Fig. '1;

Fig. 5 is a cross-sectional view of the same electromagnetic structure, along lines 5-5 of Fig. 4;

Fig. 6 is a plan view of the driving part of the same without its armature;

Fig. 7 is a cross-sectional view of the same bone condnction receiver, along lines 7-7 of Fig. 3;

along lines 3-3 of Fig. 8 is a plan view of the magnetic armature of the same bone conduction receiver;

2,804,509 Patented Aug. .27, 1957 ice Fig. 9 is a perspective view of the spacer Washer;

Fig. 10 is a view similar to Fig. 4 of a modified form of a transducer structure of the invention;

Fig. 11 is a cross-sectional view along line 11-11 of Fig. 10;

Fig. 12 is a cross-sectional view of the upper part of the structure of Fig. 10 along line 12-12 of Fig. 10; and

Fig. 13 is a view similar to Fig. 10 of a further modification of a transducer structure of the invention.

Although it is applicable to any other type of electromagnetic vibratory device, the invention will be described in connection with bone conduction receivers designed for operation as part of a wearable hearing aid small enough for inconspicuous wear on the body of the user. However, it should be understood that such bone conduction receivers of the invention are also highly effective as throat microphones for transducing the speech vibrations of the throat into an electric output which enables intelligible reproduction of speech.

Figs. 1 to 9 show one practical form of a novel hearing aid bone conduction receiver based on the principles of the invention. It comprises a relatively rigid casing structure 40 housing the internal elements of an electromechanical vibrating mechanism generally designated 50. in the form shown, (Figs. 1 to 3, 10) the relatively rigid casing structure 40 is formed of a rear wall 41 and rigid side walls 42 surrounding the interior casing space 40-1. The casing 40 has an opening at its frontal side facing the body 36 of the user, the casing opening being enclosed by a detachable contact wall 43. In the form shown, the rigid casing side wall 42 has at its open region a flat seating iace along which the similar flat border face of the contact wall 43 is seated. The casing contact wall 42 has an external generally spherical or spheroidal concave coupling surface 43-1 arranged and shaped to fit, engage and establish intimate coupling with the skin or flesh overlying the hearing inducing bone structure 36 of the body of the user, such as the mastoid eminence behind the ear of a person using the hearing aid.

The casing rear wall 41 which extends opposite to its detachable contact wall 42 is provided with a central or inner relatively thick mounting wall portion 41-1 which has mounted thereon or carries the associated elements of the internal vibrating mechanism 50 with which it forms an electromechanical transducer structure. Although it may be of any other type, the internal vibrating mechanism 59 shown is of the electromagnetic type and comprises a magnetic armature 51 having a portion affixed to the rear casing wall 41 and carrying in a vibrating condition an electromagnetic core structure generally designatd 60. The magnetic core structure 66 comprises an oblong magnetic yoke or junction plate 61 provided at its center with a cylindrical magnetic core pole piece 62 which is suitably secured thereto as by electric spot welding or by a rivet connection or by both such connections. Two permanent magnet core blocks 65 are held clamped to the opposite end regions of the oblong yoke plate 61, by an oblong magnetic pole plate 67. Suitable clamping connections, such as two screws 68 having heads engaging the yoke plate 61 and threaded end portions engaging the pole plate 67 hold the pole plate 67 clamped to the yoke plate 61.

The central core pole 62 of the electromagnetic core 60 is surrounded by coil windings 69 which are interlinked with the magnetic flux threading through the core pole 62 and across its gap spacing to the central portion of the armature 51 and then returning through the outer region 67-2 of the pole plate 67 by way of a parallel paththrough which the free end of the core pole 62 projects, the pole plate opening providing a non-magnetic or air gap 67-3 separating the pole face region 62-1 of the central. core pole 62 from the surrounding coplanal pole face of the pole plate 67. Except for the permanent magnet core block 65, the armature 51 and all other magnetic elements 61, 62 and 67 of the resiliently electro-magnetic vibrating mechanism 50 are of highly permeable magnetic material of minimized or negligible magnetic coercive force or retentivity.

In the form shown (Figs. 2, 8) the armature 51 has a relatively rigid central oblong main armature portion 52 which serves as its mounting portion and is affixed to the adjacent inward face of the inner casing rear wall portion 41-1. The armature 51 shown has two resilient arms 53 extending from diagonally opposite corner portions of the main armature portion 52, and having at their ends mounting or junction portions 54 which are suitably affixed to adjacent facing portions of the electro-magnetic core structure 60 so as to maintain the pole faces 62-1, 67-1 of the core pole 62 and the pole plate 67 spaced by a small gap of the order of .003 inch from the facing pole surface of the central armature portion 52. In the form shown, the main central armature portion 52 of the armature 51 is secured to the adjacent inner face of the mounting casing 43 by two screws 52-1 having heads seated in recesses formed in the outer wall surface of the casing rear wall 41.

In accordance with the invention, the mounting elements of the armature 51 through which it is connected to the resiliently carried electromagnetic core structure 60 are so arranged and shaped as to provide operative junction connections therebetween and also to provide stop elements for limiting the maximum vibratory excursions between the armature 51 and the resiliently carried electromagnetic core structure 60 and thereby prevent deformation of the armature beyond its elastic limit caused by a sudden impact or acceleration imparted to the relatively heavy resiliently carried magnetic structure 60, for instance, when the entire receiver is accidentally dropped on the floor.

In the form of the invention shown (Figs. 2 and 4 to 8), the end portions 54 of the two compliant arms 53 of the armature 51 constitute the mounting portions thereof which are afiixed to the adjacent facing portions of the electromagnetic core structure 60. In the form shown, the mounting end portions 54 of the two resilient armature arms 53 are arranged to terminate immediately adjacent the opposite central side surface portions of the main oblong armature portion 52 of the armature 51. Furthermore, the two mounting end portions 54 of the two armature arms 53 are provided with generally radial inward mounting extensions 55 provided with a screw seating opening or recess 56 which is sufiiciently close to the adjacent armature portion 52 so as to seat therein the shank of a screw 57 the head of which serves both to clamp the mounting end portions 54 of the respective armature arms 53 to the adjacent core pole plate 67 and also to limit the vibratory excursions of the core 60 relatively to the armature 51.

The main armature 52 is made of highly permeable magnetic sheet material and in the form shown in Figs. 4 to 11, the armature 52 and its junction arms 53 form an integral armature structure 51 of the same thickness.

To provide for the proper small gap spacing between the pole face of the main armature portions 52 and the facing pole faces 62-1 67-1 of the electromagnetic core structure 60, the mounting end portions 54 of the armature are clampingly aflixed by the clamping screws 57 to thefacing portions of the pole plate 67 across interposed spacer shims or spacer washer elements.

As explained above, the heads of the two armature junction screws 57 are arranged to serve also as stops which limit movement of the core' 60 relatively to the main armature portion 52. This is achieved by also placing between the inward face of the head of each clamping screw 57 a spacer shim or washer elements arranged to assure that a peripheral region of the head of the respective screw 57 which overlies the adjacent armature portion 52 is spaced therefrom by a small gap and operates at a stop against vibratory movement exceeding the shim thickness or the gap provided thereby. In other words, spacer shims are placed under as well as over the armature arm junction portions 54 which are aflixed by screws 57 to the pole plate.

According to the invention, the two spacer elements underlying and overlying the mounting portion 54 of each armature junction arm 53 are formed by two sections of an integral U-shaped spacer member 71 shown in detail in Fig. 9. In the form shown, the spacer member 71 is formed of a generally oblong sheet member of suitable metal, such as copper or a copper alloy, having an elongated opening 71-1 therein. The spacer sheet member 71 is folded along two spaced fold lines into a U-shaped structure having two arcuate spacer arms 72 extending from the transverse fold link 71-2 thereof.

Furthermore, each armature arm junction portion 54 is so shaped that its screw seating opening 56 constitutes only a recess confined between two junction ears 54-1 thereof which project close to the adjacent side edge of the main armature 52, and are clamped by the head of the junction screw 57 to the pole plate 67. In addition, the adjacent side edge of the main armature 52 is provided with an armature ear 52-4 projecting toward the screw seating opening or recess 46 so as to be overlapped and stopped by the peripheral region of the head of the junction screw 57 which clamps the junction arm ears 54-1fto the pole plate.

The folded shim spacer structure 71 is placed with its two arcuate spacer arms 72 on the opposite sides of each armature arm junction portion 54 which is clamped by a screw 57 to the pole plate 67. The U-shaped spacer 71 is so arranged that its transverse fold link 71-2 is seated against the end faces of the projecting junction ears 54-1 of each armature arm junction end 54 which is engaged by the head of the clamping screw 57 with which it is clamped to the pole plate 67 of the resiliently carried core 60. With this arrangement, the inwardly facing surface of the head of each clamping screw 57 overlies along a substantial arcuate region thereof the outwardly proj'ecting stop ear 52-4 of the main armature 52 at a small gap spacing therefrom, thus serving as a positive stop against further movement of the resiliently carried main magnetic core structure 60 in a direction away from the main armature 52.

Referring to Figs. 3, 4, 6, the generally circular gap region 67-3 separating the pole end of the core pole 62 from the adjoining pole plate 67 is enlarged at diammetrically opposite regions 67-3 to permit free entry of the inner shank ends of excessively long fastening screws 52-1 with which the central main armature portion- 52' is aflixed to the rear wall mounting portion 41-1. This arrangement simplifies the fool-proof assembly of the mechanism and assures that the vibratory movement of the resiliently carried core structure 60 relatively to the armature 51 is not disturbed by inaccuracies in assembling the mechanism.

One of the shorter side walls 29 of the main hollow casing 40 (Fig. 6) has also mounted therein a pair of terminal sleeves 83 arranged to detachably receive and retain a pair of terminal end plugs of the cord leads 10-1 through which the coil windings 69 of the electromagnetic core structure 60 are connected to the amplifier 12.

The terminal bushings 83 may be of any of the known type, for instance, of a type disclosed in Carlisle. et al. Patent 2,339,146 being retained in the operative position We split leaf spring 83-1 to which the respective terminal leads of the coil 69 are connected, as by soldering.

The bone conduction receiver shown may be worn on the head in a conventional way, as by means of a conventional head band 78 (Figs. 2, 7) seated on and engaging the head of the user and provided at one end with a yoke having two yoke arms 78-1 having inwardly pro jecting pivot pins seated in circular pivot recesses formed i413 the side walls 29 near the center region of the casing The main hollow casing structure 40 is oblong in shape and formed of molded synthetic resin or in general, of molded solid plastic material. The detachable contact wall 43 shown is likewise of oblong shape and likewise made of molded plastic material. The contact wall 43 is shown attached by screws 81 at its opposite shorter border regions to the flat border faces of the opposite shorter side walls 42 of the casing structure 40. The molded shorter casing side Walls 42 have embedded therein metallic bushing sleeves 81-1 (Fig. 3) with internally threaded holes shaped for clamping engagement with the threaded shanks of the clamping screws 81 of the detachable casing contact wall 43.

In order to enable more ready practice thereof but without thereby in any way limiting its scope, there will be now given constructional data of one practical form of a bone conduction receiver of the invention.

The lateral dimensions of the oblong casing 41 as seen in Fig. 2 are: maximum length .980 inch; maximum width .670 inch; and maximum height (without contact wall 43) .410 inch. The contact casing wall 43 of the receiver is .40 inch thick at the thinnest center region and has at its edge a maximum thickness of .070 inch. The dimensions of the other parts shown are correspondingly smaller.

Thetotal weight of the electromagnetic core assembly excluding the armature 52 is about 5.5 grams and the weight of the entire casing including armature 52 about 3% grams, giving the total receiver weight of 9 grams.

Figs. 10 to 12 show a modified form of armature structure 2-51 for an electromagnetic transducer device of the invention of the type described in connection with Figs. 1 to 9. The armature structure comprises a generally central flat magnetic armature 2-52 generally similar to the main armature member 52 of Fig. 8. The armature 2-52 is shown joined to the pole plate 67 of the resiliently carried core structure 60 by a resilient junction spring structure 2-60 of highly effective thinner spring sheet metal, such as beryllium copper. The junction spring structure 2-6 is shown in the form of a frame surrounding and affixed to the armature 2-52 and overlying the similarly shaped pole plate 67 of the core structure 60.

In the form shown, the junction structure 2-60 comprises an inner frame member 2-61 surrounding and afiixed to the periphery of the oblong thicker armature 2-52 and two resilient junction arms 2-52 extending from common opposite inner frame portions 2-63 of the inner frame member 2-61. The inner frame member 2-61 is formed with an angularly turned rim 2-62 fitting and secured to the peripheral border of the armature 2-52, as by welding or soldering.

In the form shown, each of the two resilient junction arms 2-53 form opposite half sections of a continuous outer frame member surrounding the inner frame member 2-61. Opposite portions thereof of the frame-like junction arms 2-53 are joined to the inner frame member 2-61 by a set of opposite common junction portions 2-63 lying adjacent to the center of the opposite shorter border sides of the oblong armature 2-52. The intermediate portion of each of the two resilient junction arm-s 2-53 is arranged and shaped to serve as a junction arm portion.

thereof 2-54 shaped similarly to the junction arm portion 54 of the armature structure of Fig. 8. The junction arm portion 2-53 of the junction structure of Figs. 10 and 11 has placed thereover the overlapping arms of a shim spacer structure 71 similar to that described in connection with Figs. l-8 and they are similarly clamped to the underlying core pole plate 67 by the heads of junction screws 57.

The opposite central portions of the inner frame member 2-61 of the resilient junction structure 2-51 are provided with the lateral stop projections 2-64 which underlie the peripheral stop region of the head of the clamping screw 57 which is arranged to stop vibratory excursions of the core structure 60 relatively to the armature 2-52 beyond the limit of the stop spacing as determined by the thickness of the spacer arm of the shim structure.

Both armature structures of the invention shown and explained in connection with Figs. 1 to 8 and Figs. 10-12 are of the beam type, in that each of these armatures has two oppositely extending junction arms joined with their two junction ends to the cooperating core structure for controlling the vibratory movement therebetween. Electromagnetic vibratory transducer devices of the invention may be also designed for operation with armatures of the cantilever type which are joined to the cooperating core structure through only one resilient junction arm.

Fig. 13 shows a cantilever type armature, generally designated 3-51 designed for cooperation with a core structure 60 of a device of the invention such as described in connection with Figs. 1-8. The armature structure 2-51 comprises a generally central flat magnetic armature 3-52 generally similar to the main armature member 52 of Fig. 8. The armature 3-52 is joined to the pole plate 67 of the core structure by only one arm 3-53 extending from one border region 3-63 of the armature 2-52 and provided with an armature junction portion 3-54 located adjacent the opposite stop border portion 3-64 of the armature 3-52. In the form shown, the armature arm 2-53 forms a continuous loop structure shaped like a frame surrounding the inner centrally disposed magnetic armature 3-52. The junction arm portion 3-54 of the look-like junction arm 3-53 is shaped similarly to the juncture arm portion 54 of the armature structure of Fig. 8 and has placed thereover the overlapping arms of a U-shaped shim spacer structure 71 similar .to that described in connection with Figs. 4-9. The junction arm portion 2-54 of the armature 2-51 of Fig. 16 is aifixed to the underlying portion of the pole plate 67 by the head of a screw 57 holding clamped thereunder the armature junction arm portion 3-54 with the two overlapping arms of the shim spacer 71 in a manner similar to that described in connection with Figs. 4-9. The peripheral region of the head of screw 57 is arranged to overlie and serve as a stop for a stop border portion 3-64 of the underlying armature 3-52 thereby limiting the vibratory excursions of the core 60 relatively to the armature to the stop spacing determined by the thickness of a spacer arm of shim structure 71.

In a co-pending application, Serial No. 299,473, filed July 17, 1952, by the applicant William F. Knauert, there are claimed the features of the invention disclosed herein directed to an inertia reaction bone conduction receiver or the like electro-acoustic transducing device, wherein the contact wall of the casing which is remote from the mounting wall of the casing carrying the internal vibratory transducer structure-has resilient elements through which it is joined to adjacent parts of the casing structure so that it vibrates relatively to the casing structure carrying the internal vibratory transducer at a resonant frequency between 2000 to 6000 :cycles or in a narrower frequency band of this frequency range.

The features and principles underlying the invention described above in connection with specific exemplifications, will suggest to those skilled in the art many other modifications thereof. It is accordingly desired that the appended claims shall not be limited to any specific features or details shown and described in connection with the exemplifications thereof.

We claim:

1. In an electromagnetic acoustic transducing device such as a bone conduction receiver, electrical windings and a magnetic core structure interlinked with said windings and having two core members arranged to vibrate relatively to each other across a gap spacing between cooperating pole faces of said two core members for translating electrical oscillations into vibratory energy and vice versa, one of said core members having at least one resilient core arm extending from a first border region thereof, which core arm has an arm end portion positioned adjacent a second border region of said one core member peripherally spaced from said first border region, an integral securing structure having a mounting portion afiixed to the other of said core members and also having an integal holder portion overlying said arm end portion for holding it afiixed to said other core memher, a further integral portion of said holder portion constituting a stop structure overlying the adjacent second border region of said one core member for limiting maximum vibratory excursions between said two core members.

2, In an electromagnetic acoustic transducing device, such as a bone conduction receiver, electrical windings and a magnetic core structure interlinked with said windings and having two core members arranged to vibrate relatively to each other across a gap spacing between cooperating pole faces of said two core members for translating electrical oscillations into vibratory energy and vice versa, one of said core members having two resilient core arms extending from one set of opposite first border regions of said one core arm, each of said core arms having an arm end portion positioned adjacent a second border region of said one core member peripherally spaced from the first border region from which it extends, an integral securing structure for each arm end portion having a mounting portion afiixed to the other of said core members and also having an integral holder portion overlying the associated arm end portion for holding it aflixed to said other core member, another integral portion of said holder portion constituting a stop structure overlying the adjacent second border portion of said one core member for limiting maximum vibratory excursion between said two core members.

3. In a transducing device as claimed in claim 1, two overlapping spacer elements of a single sheet member underlying and overlying, respectively, said arm end portion in the region in which it is held aflixed by said securing structure to said other core member, whereby said one core member is held spaced from said other core member at a spacing corresponding to the thickness of said sheet member.

4 In a transducing device as claimed in claim 3, said one core member being formed in its entirety of a magnetic body of the same thickness extending in a plane substantially parallel to the major surfaces of said spacer elements.

5. In a transducing device as claimed in claim 4, said securing structure being formed of a rod-like mounting portion atfixed to said other core member and having a wider head portion constituting said holder portion overlying said arm end portion and the adjacent second border region of said one core member.

6. In 'a transducing device as claimed in claim 2, two overlapping elements of a single sheet member underlying and overlying respectively, the arm end portion of each core arm in the region in which it is held afiixed by said securing structure to said other core member, whereby said one core member is held spaced from said other core member at a spacing corresponding to the thickness of said sheet member.

7. In a transducing device as claimed in claim 6, said one core member being formed in its entirety of a magnetic body of the same thickness extending in a plane substantially parallel to the major surfaces of said spacer elements.

8. In a transducing device as claimed in claim 7, each of said securing structures being formed of a rod-like mounting portion aflixed to said other core member and having a wider head portion constituting said holder portion overlying said arm end portion and the adjacent second border region of said one core member.

References Cited in the file of this patent UNITED STATES PATENTS 2,202,906 Hawley June 4, 1940 2,381,673 Lehde Aug. 7, 1945 2,459,325 Knowles Ian. 18, 1949 2,463,786 Lybarger Mar. 8, 1949 2,482,044 Vernier Sept. 13, 1949 2,500,541 Greibach Mar. 14, 1950 2,680,157 Wolfl June 1, 1954 2,681,389 Shaper June 15, 1954 

